Blue Ridge Low-Elevation Acidic Conglomerate Outcrop
Southern Appalachian Rocky Summit (NatureServe 2015)
East Tennessee (Cocke and Sevier counties) where restricted to generally south-facing slopes of English Mountain in the Blue Ridge Ecoregion.
Blue Ridge low-elevation acidic outcrops are small patch communities dominated by grasses and small herbs, and are surrounded by an oak/pine forest matrix. The dominant vegetation is approximately 0.1-1 m (3 ft or less) in height and restricted to shallow soil pockets and cracks in the conglomerate bedrock. The surfaces of the rock outcrop are devoid of vascular plants and are covered with lichens and mosses.
This community lies within the Level IV Ecoregion known as the Southern Sedimentary Ridges. The outcrops occur on the upper side slopes of low-elevation ridges on English Mountain. They are restricted to south and southeast-facing slopes which are steeply sloping (ranging from 35-80% slope). The elevation ranges from 600–930 m (1971–3065 ft), with most outcrops occurring near 760 m (2500 ft) above sea level. The average size for this community is approximately 7 m x 7 m, although outcrops vary in size and shape. The bedrock is Cambrian aged Cochran conglomerate. The soil is comprised mostly of cobbly residuum and/or creep deposits. It is well drained and moderately acidic.
Outcrops develop from erosional processes which expose the underlying bedrock and limit soil deposition. Rain and wind keep the rock exposed which in turn allows for high amounts of solar insolation to the outcrops. These are factors which limit the ability for vascular plant growth and help to maintain the open nature of the outcrops.
The outcrops themselves have not been researched, but J.A. Chapman (1957) documented that the forest surrounding the outcrops is comprised of mixed pine and oak trees. It includes such species as:
Pinus rigida (pitch pine)
Quercus prinus (chestnut oak)
Pinus pungens (table mountain pine)
Pinus virginiana (Virginia pine)
Quercus coccinea (scarlet oak)
Nyssa sylvatica (black gum)
Carya pallida (sand hickory)
The area immediately surrounding this community and the deepest soil pockets of the outcrops may contain such herbaceous species as:
Tephrosia virginiana (devil’s shoe string)
Pteridium aquilinum var. latiusculum (bracken fern)
Coreopsis major (coreopsis)
Sericocarpus asteroides (white-topped aster)
Andropogon scoparius (little bluestem)
Gerardia pedicularia, G. flava, G. pectinata (gerardias)
Prenanthes alba (white lettuce)
Asclepias tuberosa, A. verticillata (milkweeds)
Houstonia tenuifolia (bluets)
Amelanchier sanguinea – roundleaf shadbush
Fothergilla major – mountain witchalder
Lysimachia fraseri – Fraser’s loosestrife
Monotropsis odorata – sweet pinesap
Paronychia argyrocoma – silverling
Thermopsis mollis – Allegheny Mountain golden banner
Xerophyllum asphodeloides – eastern turkeybeard
Due to lack of study, it is unclear what, if any, invasive species may be present on these outcrops.
Associated Natural Communities
Blue Ridge sedimentary mountains dry oak/pine forests.
Presettlement Distribution and Size
It is believed the outcrops are relatively the same as pre-settlement times.
This is a rare community, limited in size and restricted to English Mountain.
Sevier County 35.878025ᵒ, -83.369731ᵒ
Cocke County 35.886845ᵒ, -83.292776ᵒ
Development of mountain summits and slopes for residential and recreational use is a major threat to this community type. English Mountain has several tracks made from the use of all-terrain vehicles. It also has a large resort and many homes which have been built at lower elevations.
Blue Ridge low-elevation acidic conglomerate outcrops are generally self-maintaining communities, although the adjacent woodlands and forests are likely, at least in part, fire dependent.
Future Research Needs
These outcrop communities are in need of extensive research to determine which species grow there, as well as document any conservation needs for these specific areas.
The Natural Vegetation of English Mountain, Tennessee, a thesis submitted to the graduate council of The University of Tennessee, by Joe Alexander Chapman (June 1957).
Chapman, J. A. 1957 The Natural Vegetaion of English Mountain, Tennessee
Hardeman, W.D., and others, 1966, Geologic map of Tennessee: Division of Geology, Tennessee Department of Environment and Conservation, scale 1:250,000
NatureServe. 2014. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1 NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org
Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov/. Accessed February/2/2015.
Checklist of Plant Species known from this community